Instant expert

Desalination

By Octavia Cade

Can turning salt water into fresh water solve the worldwide water crisis?

Credit: Laszlo Ilyes

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What is desalination?

Desalination is a method of turning salty, brackish, or recycled water into drinkable fresh water. Seawater is the most common water to undergo desalination. It is a common practice in very dry countries, where for many communities it may provide the only reliable source of potable water.

How exactly does it work?

There are two primary methods that can be used to create fresh water: 'distillation' and 'membrane' desalinisation.

Distillation involves heating salty water until the water evaporates, leaving the salt behind. The salt is removed and the water vapour collected and condensed back into a fresh liquid, ready for drinking.

The more technical but increasingly popular option of membrane desalinisation involves forcing water through a specially made synthetic membrane. The pores of this membrane are so small that while water molecules can pass through it, the larger salt molecules cannot.

So do we use desalinisation in Australia?

According to the International Desalination Association, there are 13,869 desalination plants in the world. These span across 120 countries, including Australia.

We are in fact listed as the tenth top desalinating country, producing over one million cubic metres of desalinated water a day (which does, however, pale in comparison to top-of-the-list Saudi Arabia's daily 11 million cubic metres!).

Our first large-scale plant opened only in 2006, in Perth, Western Australia. It now supplies 17 per cent of the capital city's water needs, producing 45 billion litres annually. Tugun, on the Gold Coast in Queensland, is nearing completion of its own desalination plant, and one is also being built in Sydney, set for completion in 2010. It will supply up to 15 per cent of Sydney's drinking water and be powered with 100 per cent renewable energy.

Australia is an increasingly drought-affected country, and many fresh water sources are being affected by rising salinity - a downstream impact of widespread tree felling and agricultural land use. Though desalination is an option only recently been taken up here, we will likely increasingly look towards it in the future.